<template>
  <a-tree :load-data="onLoadData" :tree-data="treeData" />
</template>

<script>
export default {
  data() {
    return {
      treeData: [
        { title: 'Expand to load', key: '0' },
        { title: 'Expand to load', key: '1' },
        { title: 'Tree Node', key: '2', isLeaf: true },
      ],
    };
  },
  methods: {
    onLoadData(treeNode) {
      return new Promise(resolve => {
        if (treeNode.dataRef.children) {
          resolve();
          return;
        }
        setTimeout(() => {
          treeNode.dataRef.children = [
            { title: 'Child Node', key: `${treeNode.eventKey}-0` },
            { title: 'Child Node', key: `${treeNode.eventKey}-1` },
          ];
          this.treeData = [...this.treeData];
          resolve();
        }, 1000);
      });
    },
  },
};
</script>
